Need Strong Batt that can fit in tight spots!

[helotaxi 5,000+ posts]

When fully charged, a cap is no strain and a battery is a very small (1A) strain. That isn't the problem. The problem is when hey are doing their job and discharging. They then must be recharged. Because of the low resistance of the cap, it becomes a drain on the alt as soon as the demand from the amps goes down into the range of what the alt can provide. A battery is the same way and multiple batteries present an even larger load.

The caps in the amp are more to filter out the ripple from the car's electrical system and to filter out the ripple from the switching power supply than to provide surge current.

I won't say that extra batteries and/or caps don't have their use in car audio. I will say that 99% of the people out there use them in the wrong situation. I see one purpose for a cap, and that is in a system where the alt is providing more than sufficient current to power the system, but needs a buffer to provide instant current for transients to allow the voltage regulator in the alt a chance to catch up to the current demand. The use I see for extra batteries is playing the system for short time with the car off. A big battery with a high skin voltage can serve the same purpose as a cap does above.

The point is, if the alt, the only SOURCE of current in the system, can't keep up with the current demand of the system and the storage devices are tapped deeply and regularly, adding more storage isn't a solution, it might temporarily mask the effect of the problem but it certainly won't fix it.

 

[knukonceptz 10+ year member]

Taxi- I agree with statement of useage above. Regarding the cap - why would it be a strain if it has such a low resistance. It just stores and discharges what is already available - if nothing is available - it still isnt a strain on the system - it is not ******* power and holding it. Maybe most folks do not realize how fast a cap charges and discharges. It is instant - speed of light movements, much faster then say the speed of sound.......

Back to the ALT not keeping up, if you play 24/7 sweeps that exceed your ALT output, yes at some point the entire system will go dead. With music, you and I know an amplifier WILL NOT draw its full potential compared to a sweep or solid test tone. I do not have a problem with upgrading ones alternator, but adding a second battery to the majority of audio systems will improve voltage (ie less spikes) and cause no long term problems to a stock charging system. As with anything improving the entire system is better then adding one part. The cars charging system should be upgraded as a whole and not just a one part fixes all solution. That said I would add the second battery before any other mod

 

[helotaxi 5,000+ posts]

Taxi- I agree with statement of useage above. Regarding the cap - why would it be a strain if it has such a low resistance. It just stores and discharges what is already available - if nothing is available - it still isnt a strain on the system - it is not ******* power and holding it. Maybe most folks do not realize how fast a cap charges and discharges. It is instant - speed of light movements, much faster then say the speed of sound.......

It does have measurable resistance and it does take time to charge. Because of its relatively low resistance though, it becomes the priority (path of least resistance) for current coming from the alt. Depending on how much of the stored energy is discharged, the cap could try to draw a pretty significant amount of current. Unless the alt is more than big enough to both power the system and recharge the cap, the cap is now a load on the alt until it is recharged. If the alt is too small, the cap will blow its load and not be of help again for quite some time, but will all along be drawing current from the alt until it is charged back up to the operating voltage of the system. It doesn't take long, but for that period of time, the alt is basically operating at a dead short.

Back to the ALT not keeping up, if you play 24/7 sweeps that exceed your ALT output, yes at some point the entire system will go dead. With music, you and I know an amplifier WILL NOT draw its full potential compared to a sweep or solid test tone. I do not have a problem with upgrading ones alternator, but adding a second battery to the majority of audio systems will improve voltage (ie less spikes) and cause no long term problems to a stock charging system. As with anything improving the entire system is better then adding one part. The cars charging system should be upgraded as a whole and not just a one part fixes all solution. That said I would add the second battery before any other mod

In this guy's situation, the alt isn't keeping up. If it was he wouldn't be getting the battery light and the voltage drop. His amps are drawing more current that the alt is putting out continuously. We know that the amps aren't drawing their max amount with music, but they don't always have to be drawing even near max amount to surpass the capacity of the alt. Put enough big amps in a system and the idle current alone is more than more modest systems draw. Get even a small output and the current goes up a ton. In alot of cases, I can see where a battery with a high skin voltage and high internal capacitance can help stabilize voltage swings, but in this case, it's still not gonna cut it at idle. The car and the amps are averaging a higher current draw than the alt can provide. No number of batteries in the world will change that. Since he problem seems to go away when the alt is spun up it would make sense that an overdrive pulley on the alt might be in order rather than a second battery. Either that or some volume control.